Properties: Gray hexagonal platelets. d 7.642. mp 585°. Single crystals have been grown by the Czochralski technique in which a hydrogen atmosphere was used to minimize the evaporation of tellurium. Since the crystals cleave readily along the (0001) basal hexagonal plane, it is mechanically easier to orient the seed so that the growth direction is in this plane rather than normal to it. The resulting crystals grow more readily along the basal plane, so that they have an oval cross section, often with a characteristic notch. All crystals so pulled are the P type. Heat of formation: -8 kcal/mol. Resistivity: 0.00033 ohm-cm. Thermal conductivities at room temp: l0 = 0.015 watt/cm-deg; le = 1.4 ´ 10-3 watt/cm-deg. Energy gap: 0.15 ev. Electron mobility: 800 cm2/volt-sec. Hole mobility: 400 cm2/volt-sec.